Opinions: 17" rims in front 18" rims in the rear - OZ Supperleggera
07-10-2006, 12:41 AM
#1
Super Member
Thread Starter
Opinions: 17" rims in front 18" rims in the rear - OZ Supperleggera
(anyone here? I'll try another thread that's a variation on the same theme as another thread I made that got no responses...)
Opinions... The rims in the pic are 17"x8" all around. How do you think this will look with the 17"x8" rims only in the front and 18"x9" rims in the rear? Look Weird using a rim w/o a lip?
There's a few cars that come from the showroom floor with different sized rims front and rear. We all know with the right tire choice of a plus size rim the outer diameter will remain the same 25" needed on this car [W202] so handling and such isn't a concern of mine. Really, just the 'look' is what I'm wondering about doing this with this kind of rim.
Why? Because
a) I want to use 255mm tires on the rear, and 255mm on a 8" wide rim will most likely have negative affect on handling as sidewalls are rounded and couuld flex more left to right easier, and the center of the tire will wear more as the tire's tread will be rounded too.
b) I bend -every- 18" rim I ever run in the fronts. Want to go back to 17" for my performance set (I'll still have a 18" show set).
c) I'm being cheap and don't want to by a whole set of 18" rims again. These 17" rims are running snows right now. I'll take two off and use them in the front with summer tires; and buy another two in 18" for the rear.
At least that's what I'm thinking about doing. Might just overlook point "a" above and run the 17" with 255 tires anyway. If consensus is it'll look dopey and not dope, that'll help my decision.
Thanx all for reading; hope to hear your thoughts.
Opinions... The rims in the pic are 17"x8" all around. How do you think this will look with the 17"x8" rims only in the front and 18"x9" rims in the rear? Look Weird using a rim w/o a lip?
There's a few cars that come from the showroom floor with different sized rims front and rear. We all know with the right tire choice of a plus size rim the outer diameter will remain the same 25" needed on this car [W202] so handling and such isn't a concern of mine. Really, just the 'look' is what I'm wondering about doing this with this kind of rim.
Why? Because
a) I want to use 255mm tires on the rear, and 255mm on a 8" wide rim will most likely have negative affect on handling as sidewalls are rounded and couuld flex more left to right easier, and the center of the tire will wear more as the tire's tread will be rounded too.
b) I bend -every- 18" rim I ever run in the fronts. Want to go back to 17" for my performance set (I'll still have a 18" show set).
c) I'm being cheap and don't want to by a whole set of 18" rims again. These 17" rims are running snows right now. I'll take two off and use them in the front with summer tires; and buy another two in 18" for the rear.
At least that's what I'm thinking about doing. Might just overlook point "a" above and run the 17" with 255 tires anyway. If consensus is it'll look dopey and not dope, that'll help my decision.
Thanx all for reading; hope to hear your thoughts.
07-10-2006, 10:28 AM
#3
Super Member
Thread Starter
Really? Even if the outer diameter of both front and rear is held @ 25" ? I thought it was only a "look thing" but it must not be somehow.
Thank you. I wish I understood why though. If you have the time, I [and I hope a few other readers] would love to know why running a 255/35-18 rear tire which has a 25" outer diameter would result in different handling characteristics then a 255/40-17 rear tire that also has a 25" outer diamter. Not being facetious at all; I really want to learn and understand this. As you can see, I invested a lot into handling in my car, so I'm always looking to understand all the black magic there is surrounding the balance of a car.
With that I mean if you note my suspension I run [click the SpeedyBenz Custom Suspension link in my sig], I have a lot of options!
My car is pretty neutral right now, even tends towards oversteer ever so slightly if I steer it like I used to before its installation [i.e. not smoothly]. When I first got it back three alignments and 1 spring swap ago when a 'corner balance' was a factor, it was oversteering pretty heavily. So just saying I can raise and lower the front and rear independantly, I have all the shock adjustments, and play with the alignment a lot more with all the adjustments I picked up.
(p.s. I cross-posted this to a few other MB boards so please ignore the dups)
Thank you. I wish I understood why though. If you have the time, I [and I hope a few other readers] would love to know why running a 255/35-18 rear tire which has a 25" outer diameter would result in different handling characteristics then a 255/40-17 rear tire that also has a 25" outer diamter. Not being facetious at all; I really want to learn and understand this. As you can see, I invested a lot into handling in my car, so I'm always looking to understand all the black magic there is surrounding the balance of a car.
With that I mean if you note my suspension I run [click the SpeedyBenz Custom Suspension link in my sig], I have a lot of options!
My car is pretty neutral right now, even tends towards oversteer ever so slightly if I steer it like I used to before its installation [i.e. not smoothly]. When I first got it back three alignments and 1 spring swap ago when a 'corner balance' was a factor, it was oversteering pretty heavily. So just saying I can raise and lower the front and rear independantly, I have all the shock adjustments, and play with the alignment a lot more with all the adjustments I picked up.(p.s. I cross-posted this to a few other MB boards so please ignore the dups)
07-10-2006, 01:56 PM
#4
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depends on the weather
well, it's really pretty simple .... let's look at what you are proposing.
All of the tires will have the same overall diameter in order to not effect traction control ABS functions and such. That means that the front tire on a 17" wheel will have a 4.0" sidewall and the rear on an 18" wheel sidewall height would be 3.5". When cornering the front tires sidewall will have approximately 15% more deflection than the rear which will cause huge amounts of understeer.
Now, I know you have seen cars running 1" larger wheels in the back before and maybe that's what gave you the idea. The Corvette is the most glaring example of this theory but, not only is the rear wheel 1" larger but, the car is designed to run a rear tire which is also 1" taller which means the sidewall heights are the same
All of the tires will have the same overall diameter in order to not effect traction control ABS functions and such. That means that the front tire on a 17" wheel will have a 4.0" sidewall and the rear on an 18" wheel sidewall height would be 3.5". When cornering the front tires sidewall will have approximately 15% more deflection than the rear which will cause huge amounts of understeer.
Now, I know you have seen cars running 1" larger wheels in the back before and maybe that's what gave you the idea. The Corvette is the most glaring example of this theory but, not only is the rear wheel 1" larger but, the car is designed to run a rear tire which is also 1" taller which means the sidewall heights are the same
Last edited by Luke@tirerack; 07-10-2006 at 02:24 PM.
07-10-2006, 02:46 PM
#5
Super Member
Thread Starter
Gotch'ya! Thank You. 
Even though the 1st CLK55 came with it, I was reluctant to use a 245mm wide tire [no matter how grippy] with the 5.4L engine and 1:3.07 gears and no LSD (my older 560SL has it and it's -great-) ... I also certainly don't want the sidewalls to blow as you set me strait on so won't use a 255mm tire with the 8" wide wheels ... and I've spent too much this year so didn't want to buy a full set of wheels right now ... so I'm not sure what I'm going to do right now.
Should just get off my keester and get my nice rims fixed. Will probably acquiesce and get 245mm in the end and use the 8" OZ....
Thanx very very much for your informed responses.
Even though the 1st CLK55 came with it, I was reluctant to use a 245mm wide tire [no matter how grippy] with the 5.4L engine and 1:3.07 gears and no LSD (my older 560SL has it and it's -great-) ... I also certainly don't want the sidewalls to blow as you set me strait on so won't use a 255mm tire with the 8" wide wheels ... and I've spent too much this year so didn't want to buy a full set of wheels right now ... so I'm not sure what I'm going to do right now.
Should just get off my keester and get my nice rims fixed. Will probably acquiesce and get 245mm in the end and use the 8" OZ....Thanx very very much for your informed responses.
07-14-2006, 10:45 AM
#6
Super Member
Thread Starter
I wanted to add something I just learned. I just read/learned of another important reason why not to run different sidewall sizes front & rear, in a great book I have on handling. Slip Angle.
As you turn the centerline angle of the wheel becomes more then that of the tire. (tire "twists" on the wheel). That difference is known as slip angle. An example the book cited was a graph that showed grip in relation to the slip angle. Grip quickly rose to 7 degrees, then peaked as 8 degrees, dropped to the same level at 9 degrees as it was at 7 degrees, then quickly dropped off from there (where the tires would be breaking loose and you'd be in a slide).
The book explained a number of things:
1) balance of a car is ensuring the slip angle of the front tires are the same as the back tires (not an easy thing it says).
2) Maximum grip for that example tire is when slip angle is between 7 and 9 degrees. (duh)
3) The tire will have as much grip when the slip angle is 9 degrees as when it is 7 degrees, however the tire will be wearing much faster @ 9 degrees, as well as quickly overheating. Over that you're in a slide.
The important thing to this dicussion however is it immediately dawned on me when I read the point in "1" above that the slip angle, meaning the 'curve' of the grip to slip angle relationship, of a tire with a 4" sidewall as it react to a turn will simply -always- be different then a tire with a 3.5" sidewall (with the assumption the 3.5" sidewall will tend to "twist" less then the 4" sidewall tire). Without exhaustive explaination, simply, the car will always be a handful and either understeer or oversteer; with a 4" tire up front, more then likely always wanting to understeer.
This stuff is kewl...
As you turn the centerline angle of the wheel becomes more then that of the tire. (tire "twists" on the wheel). That difference is known as slip angle. An example the book cited was a graph that showed grip in relation to the slip angle. Grip quickly rose to 7 degrees, then peaked as 8 degrees, dropped to the same level at 9 degrees as it was at 7 degrees, then quickly dropped off from there (where the tires would be breaking loose and you'd be in a slide).
The book explained a number of things:
1) balance of a car is ensuring the slip angle of the front tires are the same as the back tires (not an easy thing it says).
2) Maximum grip for that example tire is when slip angle is between 7 and 9 degrees. (duh)
3) The tire will have as much grip when the slip angle is 9 degrees as when it is 7 degrees, however the tire will be wearing much faster @ 9 degrees, as well as quickly overheating. Over that you're in a slide.
The important thing to this dicussion however is it immediately dawned on me when I read the point in "1" above that the slip angle, meaning the 'curve' of the grip to slip angle relationship, of a tire with a 4" sidewall as it react to a turn will simply -always- be different then a tire with a 3.5" sidewall (with the assumption the 3.5" sidewall will tend to "twist" less then the 4" sidewall tire). Without exhaustive explaination, simply, the car will always be a handful and either understeer or oversteer; with a 4" tire up front, more then likely always wanting to understeer.
This stuff is kewl...
